It is often desirable to install two or more electronic circuit boards in close proximity to each other in a relatively small area. For example, it may be desirable to place a pair of memory boards in close proximity to each other in order to minimize space utilization, while still providing discrete electrical signal paths to each circuit board. So-called card cages have been used in the past to minimize inter-board spacing. This approach, however, typically requires a bulky frame.
Furthermore, to provide the discrete electrical signal paths between a mother board and an edge connector of a circuit board, complex individual wiring is required. Such wiring has been provided by wires bundled in cables, or by ribbon cables. Such wiring arrangements are commonly subject to induced capacitive interference and cross-talk, forcing the addition of expensive and undesirable shielding and pull-down or pull-up circuits to stabilize signals or power carried in those wires. A further problem with such wiring arrangements is that the length of the conductors linking the mother board to the card cage connectors results in time delays and signal degradation.
Electrical connectors such as disclosed in U.S. Pat. No. 5,139,435 include asymmetrical rails and a card ejecting mechanism which comprises a swingable cam, pin connected to the connector body at either the end of the left or right side of the connector body. Such connectors are generally fabricated having a one piece frame made from insulating synthetic resin and having electrically conductive contact pins and terminals at a header end thereof. The contact pins at the header end project through the single piece insulative connector body to connect with a circuit card installed therein. The terminals extend beyond the header end of the single piece insulative connector body for interconnection with a circuit board or other substrate which is mated with the connector. Such single piece connector bodies are typically molded in complex molds and are not suitable, due to their relatively large size, for use with automatic assembly equipment (e.g. pick and place machines), when fabricated into electronic subassemblies. Furthermore, the asymmetry of the frame and the left or right end mounting of the cam/ejection mechanism requires that different molds be used in fabricating the left end and right end versions of the frame and ejection mechanisms. Additionally, such a cam/ejection mechanism, end mounted with no regard for symmetry, presents the likelihood of a card becoming skewed as it is removed, making removal more difficult due to the unevenness of forces applied to the card during removal.
U.S. Pat. No. 5,051,101 discloses a connector of the type for receiving and ejecting circuit cards, comprised of a separable header end with card interconnections and an ejection mechanism. The ejection mechanism is comprised of a lever (22) secured to a connecting piece (32) which connects to a guide (9) having portions that engage a circuit card being installed into or removed from the connector. The guide, among other things, serves to distribute the load of the card on the mechanisms facilitating insertion and removal. The guide in the illustrative embodiment of the '101 patent is an integrally formed molded piece of synthetic resin which includes a slider (8), engagement pieces (11), a bracket (15) and a boss (16). The guide co-acts with the operating lever which is rotatably attached by a pin offset from the center of a frame to which the ejection mechanism is attached. The offset nature of the operating lever likely creates unbalanced forces of a circuit card being installed, necessitating the force distribution function of the guide. The guide represents an additional molded or stamped part, which like other prior art connectors is not designed with regard to symmetry and results in inflexibility in fabrication and the need for additional costly tooling.